We have studied reflectance of light from human mucosal tissues and observed a new phenomenon - presence of periodic component in the reflectance spectra. We were able to observe this effect in different types of tissue such as colonic and esophageal mucosa. This periodic component can be associated with light scattered from the layer of epithelium cells, that forms the tissue-air interface. We found that the periodic component is quite informative and can provide information about nuclear size distribution in epithelium layer. This result can be very important for cancer diagnosis on early stages of disease.